Varicose veins are swollen, twisted veins that can be seen just under the surface of the skin, usually in the legs. More than 30 million people in the U.S. have varicose veins. Although the condition is often dismissed as nothing more than a cosmetic nuisance, it can cause moderate pain and has been linked to the more serious side effect of deep vein thrombosis, or blood clots in the deep veins in the body.

For the current study, researchers analyzed data on almost 500,000 people participating in the long-term UK Biobank study, looking for traits associated with risk for varicose veins, and height stood out as a strong, independent risk factor.

They followed this with a genome-wide scan of several hundred thousand people that identified 30 genetic locations, many of them involved in skeletal and blood vessel development, which further suggest tallness may be a direct cause of varicose veins.